Size effects on the mechanical behavior of nanoporous Au

Recent nanomechanical tests on submicron metal columns and wires have revealed a dramatic increase in yield strength with decreasing sample size. Here, we demonstrate that nanoporous metal foams can be envisioned as a three-dimensional network of ultrahigh-strength nanowires, thus bringing together two seemingly conflicting properties: high strength and high porosity. Specifically, we characterized the size-dependent mechanical properties of nanoporous gold using a combination of nanoindentation, column microcompression, and molecular dynamics simulations. We find that nanoporous gold can be as strong as bulk Au, despite being a highly porous material, and that the ligaments in nanoporous gold approach the theoretical yield strength of Au.     

Morphology,Oxidation, and Mechanical Behavior of Nanoporous Cu Foams

Nanoporous copper foams (65–80% porosity) are synthesized by dealloying different copper alloys, including Cu₂₀Zn₈₀, Cu₃₅Zn₆₅, and Cu₃₀Al₇₀. Ligament sizes, porosity, and oxide content are examined by scanning electron microscopy, Raman spectroscopy, and X‐ray powder diffraction to determine the nanoporous foam's structure and thermal stability. The pores and ligaments of the copper foams can range in size from 35 to 220 nm. Both parameters can be controlled by either the dealloying process or a subsequent heat treatment. The results show no copper oxide peaks for the as‐prepared samples; however, any heat treatments above 200 °C lead to the formation of Cu oxide (CuO and Cu₂O). These foams are shown to retain their structural integrity even after oxidation. A novel method is thus developed for synthesizing nanoporous Cu oxide foams by heat treating nanoporous copper.     

The effects of electricity pricing on PHEV competitiveness

Plug-in hybrid electric vehicles (PHEVs) will soon start to be introduced into the transportation sector, thereby raising a host of issues related to their use, adoption and effects on the electricity sector. Their introduction has the potential to significantly reduce carbon emissions from the transportation sector, which has led to government policies aimed at easing their introduction. If their widespread adoption is set as a target it is imperative to consider the effects of existing policies that may increase or decrease their adoption rate. In this study, we present a micro level electricity demand model that can gauge the effects of PHEVs on household electricity consumption and the subsequent economic attractiveness of the vehicles. We show that the electricity pricing policy available to the consumer is a very significant factor in the economic competitiveness of PHEVs. Further analysis shows that the increasing tier electricity pricing system used in California will substantially blunt adoption of PHEVs in the state; and time of use electricity pricing will render PHEVs more economically attractive in any state.     

Effect of arbuscular mycorrhizal colonisation on the growth and phosphorus nutrition of Populus euramericana c.v. Ghoy

Arbuscular mycorrhizal (AM) fungi are known to associate with a range of Populus species particularly in the early stages of development yet there is little information on their potential role in sustainable biomass production. Moreover, while the AM association may enhance plant establishment, growth and nutrition, different AM fungi (AMF) vary in their ability to confer such benefits. In this study we investigated the impact of four different AMF on growth and phosphorus nutrition of Populus euramericana c.v. Ghoy. Plant biomass, particularly root biomass, was generally reduced by AMF colonisation and the extent of this reduction varied with the AMF species that had colonised the roots. This growth reduction was not simply due to differences in root colonisation, which ranged from 59 to 71% by the end of the experiment at 105 d and did not vary among the AMF screened. Phosphorus content was also lower in some AMF treatments than in non-AMF controls after growth for 105 d although P concentration in aboveground tissues (stems and leaves) was higher. The possible interaction between AMF and poplar in converted arable systems is discussed.     

The adsorption and desorption of water from a carbonaceous deposit layer on the surface of stainless steel representing spent AGR nuclear fuel cladding

Spent fuel discharged from advanced gas-cooled reactor power stations carries a deposit of carbon firmly attached to the cladding surface. The fuel route involves contact with water, for cooling and transport. Long-term storage potentially includes dry storage, however, the carry-over of water entrained within the carbon deposit needs to be considered regarding the storage environment. Drying of the fuel is possible, but little is known concerning the drying characteristics of such deposits. This work reports preparation of a laboratory simulant of a carbon deposit on a fuel pin surface and measurement of its adsorption and desorption properties regarding liquid and vapour phase water. This work found that water vapour equilibration is rapid and reversible. Liquid water uptake is appreciable (up to 5.7 times the mass of carbon) and most (up to 88%) is removed on standing for 12 h. Heating removes little more. The implications for spent fuel management are discussed.     

Analysis of mass transport in the diffusional creep of polycrystalline MgO-FeO-Fe2O3 solid solutions

An analysis of mass transport in the diffusional creep of iron-doped, polycrystalline MgO was conducted. Creep regimes in which magnesium grain boundary, oxygen grain boundary, and magnesium-lattice diffusion were rate-controlling were identified. An analytical procedure was developed for the estimation of the diffusion constants for these three processes.     

Lesion site patterns in severe, nonverbal aphasia to predict outcome with a computer-assisted treatment program

OBJECTIVE: To test whether lesion site patterns in patients with chronic, severe aphasia who have no meaningful spontaneous speech are predictive of outcome following treatment with a nonverbal, icon-based computer-assisted visual communication (C-ViC) program. DESIGN: Retrospective study in which computed tomographic scans performed 3 months after onset of stroke and aphasia test scores obtained before C-ViC therapy were reviewed for patients after receiving C-ViC treatment. SETTING: A neurology department and speech pathology service of a Department of Veterans Affairs medical center and a university aphasia research center. PATIENTS: Seventeen patients with stroke and severe aphasia who began treatment with C-ViC from 3 months to 10 years after onset of stroke. MAIN OUTCOME MEASURE: Level of ability to use C-ViC on a personal computer to communicate. RESULTS: All patients with bilateral lesions failed to learn C-ViC. For patients with unilateral left hemisphere lesion sites, statistical analyses accurately discriminated between those who could initiate communication with C-ViC from those who were only able to answer directed questions. The critical lesion areas involved temporal lobe structures (Wernicke cortical area and the subcortical temporal isthmus), supraventricular frontal lobe structures (supplementary motor area or cingulate gyrus 24), and the subcortical medial subcallosal fasciculus, deep to the Broca area. Specific lesion sites were also identified for appropriate candidacy for C-ViC. CONCLUSIONS: Lesion site patterns on computed tomographic scans are helpful to define candidacy for C-ViC training, and to predict outcome level. A practical method is presented for clinical application of these lesion site results in combination with aphasia test scores.     

Intermetallic layer formation and its effect on the mechanical behavior of laminated Ta–Au composites

The tensile properties and deformation behavior of Ta–Au laminated composites processed by diffusion bonding are presented. The formation of the Ta–Au interface region was characterized using XRD, SEM and nanoindentation in order to identify the phases present. Tensile test results showed that the composition of the interface region strongly affects the overall sample behavior. The data indicates that the interface region tends to form into a stable AuTa phase. The overall material strength and ductility are then related to the composition of the intermediate interface layer.     

Construction and characterization of a recombinant vaccinia virus expressing murine intercellular adhesion molecule-1: induction and potentiation of antitumor responses

The intercellular adhesion molecule-1 (ICAM-1) has been associated with cellular migration into inflammatory sites and with facilitating interactions between lymphocytes and tumor targets in the pathway of cell-mediated cytotoxicity. More recently, ICAM-1 has become increasingly implicated in the costimulation of T cell functions, such as antigen-dependent T cell proliferation. Previous murine studies have shown that the introduction of the ICAM-1 gene into tumor cells using retroviral vectors led to enhanced antitumor responses. In this study, we report the construction, characterization, and immunological consequences of a recombinant vaccinia virus expressing murine ICAM-1. Vaccinia virus represents an attractive vector for the delivery of molecules such as ICAM-1 due to its wide host range, rapid infection, and functional expression of inserted gene products. The infection of tumor cells with this recombinant virus resulted in the expression of functional ICAM-1. Infected tumors provide accessory or secondary signals to lymphoblasts in vitro, resulting in enhanced cytokine production or alloreactive cytotoxic T lymphocyte (CTL) activity. In vivo, we demonstrated that weakly immunogenic syngeneic tumors, infected with and expressing rV-ICAM-1, were rejected by immunocompetent hosts. Furthermore, immunization with rV-ICAM-1-infected tumors resulted in the rejection of subsequent tumor challenge, providing evidence for recall response and immunological memory. These studies demonstrated the utility of a recombinant vaccinia virus to deliver and efficiently express ICAM-1 molecules on tumor cells for potential gene therapy and recombinant approaches to cancer immunotherapy.